Physics - electrons, waves and photons

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jpopat
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213447
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Physics - electrons, waves and photons
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2013-04-14 15:53:54
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Physics electrons waves photons
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Physics - electrons, waves and photons
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  1. Ampere
    A current or rate of flow of charge of one coulomb per second
  2. Charge
    A fundamental property of matter and may be positive or negative
  3. Coulomb
    A unit of charge produced when a current of 1A flows for 1s
  4. Kilowatt hour
    A unit of energy produced when a device rated at a power of 1kW is used for 1 hour (equal to 3.6 MJ)
  5. Kirchhoff's 1st Law
    The sum of currents entering a junction is equal to the sum of currents leaving a junction (conservation of charge)
  6. Kirchhoff's 2nd Law
    The sum of emf around a loop is equal to the sum pd round the loop (conservation of energy)
  7. Mean drift velocity
    The average velocity that a charged particle attains due to an electric field
  8. Terminal pd
    The voltage across the ends of a battery and is equal to the emf-lost volts
  9. Ohm
    The resistance of a conductor through which a current of 1A is flowing when the pd across it is 1v
  10. Ohm's Law
    The current though a metallic conductor is directly proportional to the potential difference across it provided there is no change in the physical conditions (eg temperature) of the conductor
  11. The resistance of an LDR
    As light intensity increases, resistance of the LDR decreases
  12. Photon
    A quantum of energy of electromagnetic radiation (E=hf)
  13. Resistivity
    (Resistance x cross sectional area) / length
  14. Planck's Law
    E=hf
  15. Resistance
    Pd across conductor / current across conductor
  16. Potential difference (pd)
    Between two points in a circuit is the amount of energy in joules changed into other forms per coulomb of charge that passes from one point to another
  17. Power
    Rate of conversion of energy in watts (= joules per second)
  18. Volt
    One joule of energy per coulomb of charge
  19. Work function
    The minimum photon energy needed to eject a photoelectron from a metal
  20. Current
    The rate of flow of charge
  21. EMF
    Electrical energy transferred per unit charge as the charge passes through a source
  22. Internal resistance
    Is responsible for energy lost in a cell when a current flows though it
  23. Threshold frequency
    The minimum frequency of incident radiation needed to release photoelectrons
  24. Coherence
    Constant phase difference
  25. Laws of reflection
    • 1. The reflected ray, the incident ray and the normal are coplanar
    • 2. The angle of reflection is equal to the angle of incidence
  26. Malus' Law
    I = 
  27. UV - A
    Causes sun tan
  28. UV - B
    Causes sunburn and skin cancer
  29. Wavelength of visible light
    • m
    • m
  30. Intensity
    • Intensity = power / surface area
    • Intensity  amplitude2
  31. For a maximum the path difference...
    Is equal to a whole number of wavelengths
  32. For a minimum the path difference...
    Is equal to an odd number of half wavelengths
  33. Transverse wave
    The direction of particle oscillation is perpendicular to the direction of energy travel
  34. Longitudinal wave
    The direction of particle oscillation is parallel to the direction of energy travel
  35. Wavelength
    The distance between two consecutive points which are in step
  36. Displacement
    How far and in which direction each particle is from it's central undisturbed position
  37. Amplitude
    The maximum displacement that the particles obtain from their central undisturbed position
  38. Frequency
    The number of complete cycles of oscillation performed per second
  39. Period
    The time taken to perform one complete cycle of oscillation
  40. Relationship between frequency and period
    f = 1/T
  41. Wave speed
    V = f 
  42. In phase
    Two waves are said to be exactly in phase if all the crests of one exactly align with the crests of the other
  43. Out of phase (180•)
    If the crests of one wave line up with the troughs of another
  44. Polarisation
    A property of transverse waves where all the oscillations are in the same plane
  45. Pitch
    Of a sound depends on frequency
  46. Loudness
    Of sound is determined by the amplitude of the vibrations
  47. The principle of superposition
    The vector addition of the displacements of two or more waves that meet

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